The present invention relates to vortex flowmeters. More specifically, the invention relates to vortex flowmeters for use with a pressurized process fluid.
Vortex flowmeters are commonly used in industrial processes to measure a flow of a process fluid, such as slurries, liquids, vapors and gases of chemicals, petroleum, pharmaceuticals, food and other fluid-type plant processes. Typically, vortex flowmeters utilize a shedding bar placed in a fluid flow to cause or generate vortices on opposite sides of the shedding bar. The frequency of vortex shedding for a shedding bar is directly is proportional to the velocity of flow in the process fluid. Therefore, vortex flowmeters sense the fluctuating pressures caused by the generated vortices to determine the velocity of the process fluid flow. Example vortex flowmeter implementations can be found in U.S. Pat. No. 4,926,695 to Rosemount, Inc. of Eden Prairie, Minn. on May 2, 1990, U.S. Pat. No. 5,343,762 to Rosemount, Inc. of Eden Prairie, Minn. on Sep. 6, 1994, both of which are commonly assigned with the present application.
Typically, a sensing device of a vortex flowmeter is coupled to, yet isolated from, the process fluid by a flexure. Often, a cavity is defined between the sensing device and the flexure. From time to time, a sensing device can fail. Since the sensing device is isolated from the process fluid by the flexure, the sensing device is replaceable without depressurizing the process fluid. However, replacing the sensing device while the process fluid is under pressure can be unsafe. In the event that the sensing device fails, it is impossible to know if the flexure that is in communication with the process fluid has also failed. If the flexure has also failed, pressurized process fluid will be contained in the cavity and upon removal of the sensing device can spray out.